Free spin fastener and connection system

ABSTRACT

A fastener and a fastener system using the fastener are disclosed. The fastener has an elongated shank having a thread formed at one end and a annular recess formed adjacent the threaded portion to define a leading and trailing abutment surface. The thread guides the fastener into engagement with one or more components having thread engagement features and the annular recess permits the free spinning of the fastener without further tightening after the thread engagement features have advanced past the thread. The fastening system includes the fastener and a component to be fastened having a passageway for accepting the fastener formed by at least two flanges engageable in the thread and engageable in the annular recess of the fastener.

TECHNICAL FIELD

The present disclosure relates to fastener systems, and moreparticularly to fastener system for securely holding two componentstogether against undesired separation while preventing excessive strainlevels within the components.

BACKGROUND

Many components are attached to one another by locks integrally formedin one of the components. Such integrally formed locks keep the numberof parts required for assembly low and allow some control of stresslevels in the components by dimensional control of the components.However, they do not facilitate separation of the components whenservicing is required. When an integrally formed lock is damaged, itrequires replacement or rework of the component from which it is formed.Furthermore, if the lock is integrally formed with one of the componentsbeing fastened, it must be formed of the same material as thatcomponent, which results in a compromise in the choice of materialbetween those having characteristics most appropriate for the functionof the component and those most appropriate for the locking feature.

Alternatively, many components have been attached to one another by afastening pin that extends through apertures in the two components andis headed on one end to abut a surface of one component. The fasteningpin is typically threaded into the material of the other component. Forsome installations, particularly where a threaded fastener is threadedinto a plastic component, the components may be damaged if excessivetorque is applied. Such fastening assemblies may require specializedtooling, such as sensitive torque limited tightening equipment, forassembly or disassembly of the components for those installations wherecontrol of the amount of stress experienced by the components beingfastened is critical. Furthermore, systems relying on threaded lockingsystems may be less reliable than abutment-type locking systems when thecomponents are used in environments where significant vibration isexperienced.

For example, in a traditional automotive bussed electrical centerconnection system, there are a series of male blades used to connect thevarious wiring harnesses to the vehicle. Since the bussed electricalconnection-type harness connection is comprised of plastic components,it is considered a “soft” mechanical joint and the bolt is used as amechanical assist mechanism and not as a compression force driver. Thetorque limits for such bussed electrical connection-type harnessconnections may be in the range of three to six newton-meters (3-6 nm),significantly lower than the torque range of typical other fastenersused in vehicle assembly, thus requiring special tools to prevent damageto the comparatively soft plastic components.

Another approach used in some connections is to use a fastening systemshaving an elongated headed and threaded pin and threading an additionalcomponent, such as a nut, onto the back side of the pin. Still anotherapproach is using and elongated member and deforming it on the back sideof the components to be fastened. These approaches may be inconvenientor impossible for many installations, such as the bussed electricalconnection-type harness connection described above, because they requireaccess to the backside of the fastened assembly, which may beunavailable or difficult to access. They also still may require torquelimiting equipment to avoid excessive stress levels.

In light of the foregoing, a need has arisen for a fastener system thatis easy to assemble without specialized tooling, facilitates low costservicing of the components being fastened, minimizes stressesexperienced by the components, and provides for a secure assembly of thecomponents in an environment susceptible to vibration.

BRIEF SUMMARY

A fastener system includes a shank having a leading portion and atrailing portion, wherein a threaded portion formed on the leadingportion defines a first outer diameter. An annular recess is formedbetween the threaded portion and the trailing portion of the shankdefining a second outer diameter smaller than the first outer diameter.A leading abutment is formed at the leading end of the annular recess,the threaded portion of the fastener shank terminating at the leadingabutment, and a trailing abutment formed on the trailing end of theannular recess.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample in greater detail with reference to the attached figures, inwhich:

FIG. 1 is a perspective view of an exemplary assembly of componentsusing the fastener and fastening system;

FIG. 2 is a sectional view through the assembly of components of FIG. 1illustrating some features of the fastener and the fastening system;

FIG. 3 is a perspective view of the exemplary fastener used in theassembly of components of FIGS. 1 and 2;

FIG. 4 is an elevational view of the fastener of FIG. 3;

FIG. 5 is an enlarged perspective view of the leading portion of thefastener of FIGS. 3 and 4;

FIG. 6 is a top plan view of a female fastening component for use inassociation with the fastener of FIGS. 3-5;

FIG. 7 is a bottom plan view of the female fastening component of FIG.6;

FIG. 8 is a perspective view of one passageway segment of the femalefastening component of FIGS. 6 and 7;

FIG. 9 is an elevational view of the passageway segment of FIG. 8; and

FIG. 10 is an enlarged cross-sectional partial view of the fastenerassembly showing the fastener of FIGS. 3-5 engaged with the femalefastener component of FIGS. 6-9.

DETAILED DESCRIPTION

Referring now to the discussion that follows and also to the drawings,illustrative approaches to the disclosed systems and methods are shownin detail. Although the drawings represent some possible approaches, thedrawings are not necessarily to scale and certain features may beexaggerated, removed, or partially sectioned to better illustrate andexplain the present invention. Further, the descriptions set forthherein are not intended to be exhaustive or otherwise limit or restrictthe claims to the precise forms and configurations shown in the drawingsand disclosed in the following detailed description. The presentdisclosure provides a fastener and a fastening system that facilitatesproviding a reliable and durable assembly while minimizing the stressexperienced by the components being fastened. As will be described ingreater detail below, while the fastener and fastening system areillustrated in the exemplary embodiment in the drawing as a system forfastening components of a wiring harness, the fastener and fasteningsystem may be used for a wide variety of fastening applications.

There are many applications requiring a fastening assembly 10 (FIGS. 1,2 and 10) for holding two or more components together in a reliablemanner without subjecting the components to excessive stress. Forexemplary purposes, the fastener assembly 10 illustrated in FIGS. 1 and2, has a bolt or fastener 20 used for holding together an uppercomponent 22 and a lower component 24 of a vehicular bussed electricalcenter assembly. A female fastening component 26 (FIG. 2) for engagingthe fastener 20 is incorporated into the lower component 24 of theelectrical center assembly in the example illustrated.

Refer now to FIGS. 3-5 illustrating details of the fastener 20. Thefastener 20 has an elongated shank 30 defining a longitudinal axis 32(FIG. 4), a leading portion 34 and a trailing portion 36. The leadingportion 34 is provided with a thread 40 (a threaded portion) forengagement with the female fastening component 26 (FIGS. 2 and 6-10) ina manner described later herein in detail. The thread 40 is designed soas to have a valley and pitch proportioned to accept a thread engagementstructure, described later, of the female fastening component 26, alsodescribed in detail later. In the example illustrated, the thread 40 isa large three-quarter (¾) turn thread.

The fastener 20 is further provided with an annular recess 46 formedadjacent to the thread 40 in the trailing portion 36 of the elongatedshank 30. The annular recess 46 has an outer diameter less than theouter diameter of the thread 40. In the example illustrated, the annularrecess 46 further has an outer diameter approximately equal to the innerdiameter of the thread 40. The annular recess 46 defines a leadingannular abutment surface 48 where threads 40 terminate as well as atrailing annular abutment surface 50 opposite the leading annularabutment surface 48. The outer diameter and the longitudinal length ofthe annular recess 46 between surfaces 48 and 50 are also proportionedto accept at least one inwardly extending lip, described later, of thefemale fastening component 26.

The elongated shank 30 has an intermediate annular enlarged portion orintermediate head 52 having a reduced diameter trailing portion 54extending longitudinally in the trailing direction from the annularrecess 46. The intermediate head 52 has an outer diameter greater thanthe inner diameter of the thread 40 and is proportioned to engage thewalls of a passageway in the female fastening component 26.

The elongated shank 30 may be provided with other engagement featuressuch as enlarged annular portions, annular recess 46, and other featuresfor providing specialized functions like engagement, connection, andabutment as required by the specific components being fastened togetherby the fastener 20. In the example illustrated, as shown in FIGS. 3 and4, the elongated shank 30 of the fastener 20 may be provided withenlarged annular portions 56 and 58 and annular recess 46 forcooperation or engagement with features of the upper component 22 orlower component 24 (FIG. 2) of the assembly of components being joinedby the fastener 20.

As shown in FIGS. 1-4, the fastener 20 is provided with a head 64 at itstrailing end portion 36. The head may provide an abutment surface forengagement with one of the components being joined by the fastener 20.The head 64 may also provide a tool engagement feature, such as a maleor female tool engagement feature for accepting a screw driver, wrenchor other fastener installation tool, not illustrated.

FIGS. 6-9 illustrate details of an exemplary female fastening component26. As best shown in FIGS. 6 and 7, the female fastening component 26includes a main body 70 having a plurality of downwardly extendingflanges or passageway segments 72 (FIGS. 8 and 10) that cooperate toform an elongated passageway 74 through the female fastening component26 for the fastener 20. As best shown in FIGS. 8 and 9, each passagewaysegment 72 has an arcuate surface 76 that cooperates with one or moreother passageway segments 72 to define a circular cross section for theelongated passageway 74. The arcuate surface 76 is also curvedlongitudinally to define a gradually reducing outer diameter for theelongated passageway 74. An inwardly extending lip 78 is formed at theleading edge of each passageway segment 72. Each inwardly extending lip78 provides a thread engagement structure for engagement with the thread40 and the annular recess 46 (FIGS. 2, 3, 4 and 10) of the fastener 20.

Refer now to FIG. 10 illustrating the fastener 20 engaged with thefemale fastening component 26. For installation, the leading end of thefastener 20 is inserted into the elongated passageway 74 until thethread 40 encounters the inwardly extending lips 78 of the passagewaysegments 74 of the female fastening component 26. The fastener 20 isrotated to advance the thread 40 past the inwardly extending lips 78,which may be facilitated by a small deflection of the passagewaysegments 74. As the fastener 20 is advanced along the elongatedpassageway 72, the intermediate head 52 advances adjacent the inwardlysloping arcuate surface 76 and engages the arcuate surface. The arcuatesurface 76 exerts an increasing force on the intermediate head 52resisting the continued advancement of the fastener 20 along theelongated passageway 74. The fastener is rotated to pull the assemblytogether until the thread 40 passes the inwardly extending lips 78 andthe lips enter the annular recess 46 in the elongated shank 30 of thefastener 20.

Once the thread 40 of the fastener 20 has passed the inwardly extendinglips 78 and the lips have fully entered the annular recess 46, thefastener 20 may spin freely without further tightening of the assembly.At this point, the leading annular abutment surface 48 of the elongatedshank 30 engages the inwardly extending lips 78. In this way, the boltor fastener 20 can spin freely after assembly regardless of any appliedtorque.

In the illustrated embodiment, when the lips have fully entered theannular recess 46, the arcuate surfaces 76 of the passageway segments 72exert sufficient force on the intermediate head 52 to bias the inwardlyextending lips 78 in a fixed position against the leading annularabutment surface 48 of the elongated shank 30. The leading annularabutment surface 48 inhibits the inwardly extending lips 78 fromreentering the thread 40, thereby inhibiting the undesired uncoupling ofthe components if the fastener is rotated in the direction opposite thetightening direction.

In the example illustrated, the female fastening component 26 is formedof a plastic material and the passageway segments 72 have apredetermined flexibility designed to facilitate the passage of thefastener 20 along the elongated passageway 74 during a fasteningoperation, while having sufficient stiffness to prevent theunintentional disengagement of the inwardly extending lip 78 from theannular recess 46 after assembly is complete.

An additional advantage of the inherent torque limiting characteristicof the fastener system described above is that components of theassembly do not need to be designed to withstand the higher level oftorque or compression which they might unintentionally experience withprior designs, regardless of the potential torque output of thetightening equipment used. For example, the fastener 20 used for avehicle bussed electrical connection can be made from an inexpensive diecast zinc alloy using a die cast manufacturing process without requiringthe use of a special torque limiting tool. By eliminating the excessivetorque or stress associated with traditional connection systems, thefastener becomes compatible with commonized tools.

It will be appreciated that while the fastener system has been describedusing an exemplary bussed electrical service assembly; the fastenersystem described herein has broad applications for fastening a varietyof components. The foregoing embodiments were chosen and described inorder to illustrate principles of the methods and apparatuses as well assome practical applications. The preceding description enables othersskilled in the art to utilize methods and apparatuses in variousembodiments and with various modifications as are suited to theparticular use contemplated. In accordance with the provisions of thepatent statutes, the principles and modes of operation of this inventionhave been explained and illustrated in exemplary embodiments.

It is intended that the scope of the present methods and apparatuses bedefined by the following claims. However, it must be understood thatthis invention may be practiced otherwise than is specifically explainedand illustrated without departing from its spirit or scope. It should beunderstood by those skilled in the art that various alternatives to theembodiments described herein may be employed in practicing the claimswithout departing from the spirit and scope as defined in the followingclaims. The scope of the invention should be determined, not withreference to the above description, but should instead be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled. It is anticipated andintended that future developments will occur in the arts discussedherein, and that the disclosed systems and methods will be incorporatedinto such future examples. Furthermore, all terms used in the claims areintended to be given their broadest reasonable constructions and theirordinary meanings as understood by those skilled in the art unless anexplicit indication to the contrary is made herein. In particular, useof the singular articles such as “a,” “the,” “said,” etc. should be readto recite one or more of the indicated elements unless a claim recitesan explicit limitation to the contrary. It is intended that thefollowing claims define the scope of the invention and that the methodand apparatus within the scope of these claims and their equivalents becovered thereby. In sum, it should be understood that the invention iscapable of modification and variation and is limited only by thefollowing claims.

1. A fastener comprising: a shank having a leading portion and atrailing portion, a threaded portion formed on the leading portiondefining a first outer diameter; an annular recess between the threadedportion and the trailing portion, wherein the annular recess defines asecond outer diameter, smaller than the first outer diameter; a leadingannular abutment formed at the leading end of the annular recess, thethreaded portion terminating at the leading annular abutment, and atrailing annular abutment formed on the trailing end of the annularrecess.
 2. The fastener of claim 1, further comprising a head on thetrailing portion of the shank.
 3. The fastener of claim 1, furthercomprising a tool engagement feature formed at the trailing portion ofthe shank.
 4. The fastener of claim 3, wherein the tool engagementfeature is selected from a male engagement feature and a femaleengagement feature.
 5. The fastener of claim 1, wherein the head has atleast one annular engagement structure capable of engaging an engagementsurface of a component being fastened by the fastener.
 6. The fastenerof claim 1, wherein the thread portion defines an inner thread diameterapproximately equal to the second outer diameter.
 7. The fastener ofclaim 1, wherein the threaded portion defines a thread having agenerally rectangular shape.
 8. The fastener of claim 1, wherein thethread portion comprises a three-quarter turn thread.
 9. A fastenercomprising: a shank having a leading portion and a trailing portion; athreaded portion formed on the leading portion defining a first outerdiameter; a trailing portion of the shank having a second outer diameterless than the first outer diameter; an intermediate portion of the shankbetween the leading portion and the trailing portion, the intermediateportion having a third outer diameter larger than the first outerdiameter; an annular recess between the threaded portion and aintermediate portion of the shank defining a fourth outer diametersmaller that the first outer diameter, a leading annular abutment formedat the leading end of the annular recess, the threaded portionterminating at the leading abutment; and a trailing annular abutmentformed on the trailing end of the annular recess.
 10. The fastener ofclaim 9, further comprising a head on the trailing portion of the shank.11. The fastener of claim 10, further comprising a tool engagementfeature formed at the head.
 12. The fastener of claim 9, wherein thetrailing portion of the shank has at least one annular engagementfeature having an outer diameter larger than the second outer diametercapable of engaging a engagement surface of a component being fastenedby the fastener.
 13. The fastener of claim 9, wherein the trailingportion of the shank is unthreaded.
 14. The fastener of claim 9, whereinthe thread portion defines an inner thread diameter approximately equalto the third outer diameter.
 15. A fastening system comprising: a femalefastener component having a main body and an elongated passageway havingan inner wall with a first inner diameter and an inwardly extending lipdefining a second inner diameter smaller than the first inner diameter;and a male fastener component comprising a shank having a leadingportion and a trailing portion including: a thread formed on the leadingportion, the thread having a first outer diameter between the first andsecond inner diameters, the threaded portion being engageable with theinwardly extending lip of the female fastener component for threadableengagement therewith such that the male fastener is capable of beingadvanced in the leading direction relative to the female fastenercomponent along a longitudinal axis by rotating the shank; an annularrecess between the threaded portion and a trailing portion of the shankdefining a second outer diameter smaller that the first outer diameter,the annular recess being engageable with the inwardly extending lipafter the threads have been advanced along the longitudinal axis pastthe end of the threads; and an annular head formed one portion of theshank trailing of the annular recess, the annular head having a thirdouter diameter between the first and second inner diameters, the annularhead being capable of engaging the inner wall of the female fastenerwhen the inwardly extending lip is engaged in the annular recess of theshank; wherein the male fastener component may spin freely relative tothe female fastener component without further advancement of the malefastener component in the leading direction when the outwardly orientedlip is within the annular recess, thereby permitting the free spinningof the male fastener component without a further tightening of theconnection with the female fastener component.
 16. The fastener systemof claim 15, wherein the elongated passageway is formed by a pluralityof elongated passageway segments.
 17. The fastener system of claim 16,wherein the elongated passageway segments are flexible.
 18. The fastenersystem of claim 15, wherein the shank further comprises an annularabutment formed at the leading end of the annular recess, the threadsterminating at the leading abutment, the leading abutment beingengageable with the outwardly oriented lip of the female fastercomponent to inhibit the longitudinal movement of the shank when theoutwardly oriented lip is engaged with the annular recess, therebyinhibiting the re-entry of the outwardly oriented lip into the threadand permitting the free spinning of the male fastener without aloosening of the connection with the female fastener component.
 19. Thefastener system of claim 15, wherein the elongated passageway furthercomprises an inwardly oriented sloping surface adjacent the inwardlyextending lip for engagement with the annular head of the male fastenercomponent.
 20. The fastener system of claim 15, wherein the shankfurther comprises an elongated trailing shank portion trailing of theannular head.
 21. The fastener of claim 20, further comprising aterminal head on the elongate trailing shank portion.
 22. The fastenerof claim 21, further comprising a tool engagement feature formed in thehead.
 23. The fastener of claim 15, wherein the threaded portion definesa thread having a generally rectangular shape.